What pre-treatment step is required before electrophoresis for CSF and urine samples?

• A. Centrifuged first
• B. Heat inactivation
• C. Dialysis
• D. Filtration

Answer: (A)

Before electrophoresis, you want a clear, particulate-free sample. CSF and urine can contain cells, debris, and other particulates that disrupt protein separation, cause streaking, or clog the gel or capillary. Centrifugation pelts those solids into a pellet, leaving a clean supernatant that contains the soluble proteins ready for accurate separation. This pre-treatment improves resolution and reliability of the protein patterns seen after electrophoresis.

Heat inactivation would denature proteins and distort the results, so it’s not appropriate. Dialysis removes salts and small molecules, which can alter the protein pattern, making it unsuitable as a standard pre-step for this purpose. Filtration might remove particulates but can also remove or bind proteins depending on the membrane, risking loss of target analytes. Thus, spinning down the sample to obtain a clear supernatant is the appropriate first step.